Recently played a skirmish on the roughness map and for some reason there are two oils that can not be obtained on the center most set of hills. Maybe smooth out the shallow cliffs that block the path to them?

I did it intentionally. Nowadays i believe that the map overally flawed, because it has way more oil than normal (around 20/player), and because the oil is spread out widely around the map. Which means that victory heavily depends on the player's ability to multitask many trucks in the early game to capture the oil as soon as possible for immediate economic advantage. However, blocked oils require more than just trucks to capture - you also need tanks to clear the path, which slightly mitigates this effect by delaying any action around these derricks to a later phase of the game. So i'm rather against fixing it, but i don't care about that too much because nowadays i believe that the map is anyway very casual; if you think it takes away fun most of the time, please fix it.